Motion sickness, a common problem in travellers by automobile, train, air, and particularly sea, usually causes mild to moderate discomfort but in severe cases can be incapacitating.
It affects up to half of children travelling in automobiles or airplanes and almost 100% of boat passengers in very rough seas.
Motion sickness is more common in women, especially during pregnancy or menstruation, children age 2-12, and in persons who have migraine headaches, but little is known about individual susceptibility.
Symptoms of motion sickness
Sensation of head position and movement is generated in the semicircular canals (angular acceleration or rotation) and otolith organs (vertical acceleration) in the inner ears and carried to the central nervous system via cranial nerve VIII.
The signs and symptoms of motion sickness occur when sensory information about the body's position in or movement through space is contradictory or contrary to prior experience. Resulting signs and symptoms include dizziness, nausea, vomiting, pallor, and cold sweats.
Travellers who are susceptible to motion sickness can minimize symptoms by choosing seats with the smoothest ride (front seat of a car, forward cars of a train, and the seats over the wings in an airplane), focusing on distant objects rather than trying to read or look at something inside the vehicle, minimizing head movement, and if necessary lying supine.
Treatment of motion sickness with medication
Medications that may ameliorate symptoms of motion sickness include scopolamine (available in both patch and oral form), oral meclizine, dimenhydrinate, diphenhydramine, and promethazine.
Choice of medication is based on trip duration, underlying medical conditions, and concerns about sedation. Scopolamine patches are appropriate for longer voyages and should be applied 4 hours before departure and changed every 3 days if needed. Oral scopolamine is effective for 6-8 hours and can be used for short journeys or for the interval between application of the patch and onset of effectiveness.
Other oral medications are efficacious for several hours and can also be used for shorter journeys.
Oral medications should be started 1 hour before departure.
All these medications can impair alertness and must be used with caution by persons operating vehicles or heavy machinery. This effect is additive with alcohol and is least severe with scopolamine.
In addition, because these drugs all have anticholinergic properties, they should be avoided in travellers with narrow-angle glaucoma, pyloric obstruction, or prostatic hypertrophy and should be used with caution in those with asthma and cardiovascular disease.
Side effects include dry mouth, blurred vision (especially for persons with hyperopia), and bradycardia. Promethazine primarily decreases nausea and has been combined with ephedrine (25-50 mg) to decrease sedation. Only dimenhydrinate and diphenhydramine are recommended for use in children. They may cause paradoxical excitation and should not be used in children <2 years of age.
Non-pharmacologic treatment of motion sickness
Nonpharmacologic methods for motion sickness may benefit some persons but have not been proven consistently effective.
High levels of ginger have been helpful in some people.
Pressure on the P6 acupuncture point of the wrist provides relief of nausea in pregnancy and after chemotherapy, but evidence for efficacy in motion sickness is contradictory.